Two weeks ago I installed OSX 10.8 on my Mac mini. After that, my system started to hang a lot, so I tried to erase it and install OSX 10.7 again. I used carbon Copy Cloner to make the bootable USB and it can load successfully on another Macbook. However, on my Mac mini, when I press on the option button to select the USB, it loads the white screen with a ban symbol at the center of the screen. After a moment, my machine automatically shuts down. Does anyone know how to solve this problem?
Edit: this is exactly the problem I have now http://forums.macrumors.com/archive/index.php/t-1207168.html
Update 1: the hdd seems ok (from disk utility). I restored the booting partition by disk utility (drag the dmg file to that partition). After restarting and using that partition to boot, prohibited symbol is still there
Update 2: This is my disk utility 
I tried to erase the booting partition again and then, got the kernel panic (cpu 2 caller bla bla bla ). This is so ridiculus when I have a thing called "bootable" usb but cannot do anything to save the system. After the panic, my mac sounds 3 beeps in a row continuosly. I turned off the power after all.
